Soft and flexible gold microelectrodes by supersonic cluster beam deposition and femtosecond laser processing

Soft and flexible microelectrodes are fabricated and patterned in a novel approach integrating supersonic cluster beam deposition (SCBD) of gold nanoparticles onto Polydimethylsiloxane (PDMS) followed by femtosecond (fs) laser processing. SCBD of gold nanoparticles in PDMS forms a nanocomposite film with mechanical properties similar to those of the elastomeric substrate. Electrically neutral metallic nanoparticles penetrate the polymeric matrix and distribute randomly up to a depth of a few hundred nanometers forming a path of ohmic conduction. High resolution patterning on soft substrates is a major challenge that was overcome by femtosecond laser ablation of micrometer lines with relatively very little thermal damage. Microelectrodes were fabricated with a width down to 3 μm. The printed metal line sheet resistance was 480 Ohm/square for the 100 nm thick film and 210 Ohm/square for the 200 nm thick film. The calculated average film specific resistivity was found to be 2.5–2.6mΩ·cm. It is ~3 orders of magnitude higher than that of physical vapor deposited gold; therefore, it is not suitable for high current interconnects but sufficient for low-current signal transmission such as for electrical and electrochemical biosensors.